Gas Boiler very slow to heat Water?

We have moved into a new house and we are thinking our water is not heating as fast as it should be.

We have a pump shower that is feeding from the main hot water tank. We are currently attempting to heat the hot water tank with gas (we also have an immersion; however, we have not used this yet ...the thinking being that gas should be cheaper).

• At first we had the gas on for 2hrs 30mins in the morning to heat the water; however, the water ran cold towards the end of the second shower.
• We then tried timing the gas on for 3hrs to heat the water and this was sufficient for 2 showers.

Surely it should not be taking this long to heat our tank. Any thoughts would be much appreciated.

Notes:

• We have the thermostat on our hot water tank set the maximum.
• We are using gas also for our central heating and it heats up all of our radiators very quickly (two zones that are controlled by thermostats).
• Also, I assuming the bath/sink control is solely for heating the water via the immersion (this is currently set to "Sink")

How big is the cylinder? how big is the pump?

Look at your cylinder, you will see two pipes entering the side of it, they will run parallel. see the bottom pipe, there should be a red wheeled valve on it. This is for balancing the heating system, (it restricts flow of hot water to cylinder coil) open it up a bit and it should improve things on the cylinder side.

Thanks for the info DavyJones. I'll check that red wheeled valve on it when I get home from work and will let you know how I get on. Thanks again!

If the water is running cold before the end of the second shower then the problem probably isn't how hot the water is, it's how much hot water you've got - and if you've got the switch set to "sink" then it's only heating half the tank. You need to flip it to "bath" to heat the whole tank.

But aside from that, putting on the gas for even two and half hours just for two (twenty minute?) showers is going to be incredibly expensive, especially with gas and electricity prices shooting up. Do you have to do that even when you don't have the heating on anyway? (I'm assuming when you do have the heating on the water in the cylinder is heated at the same time).

You'd save yourself a fortune if you got an instant shower - then for forty minutes worth of showers you'd only be heating the water for, you've guessed it.... forty minutes!

DubGem, the problem is definitely the amount of hot water that we have (the actually temperature of the hot water when it is available is fine).

Does the sink/bath switch actually apply to the hot water tank when it is being heated by gas? I'm confused about this - I was under the assumption that this switch only applies when you are using the immersion (i.e. electricity) to heat the water. Is this incorrect?

I agree that putting the gas on for 3 hours to heat the water is ridiculous from an expense point of view...thats why I'm trying to establish what our problem is. After paying good money for our pump shower we want to be able to enjoy it rather than having to revert to the instant electric shower.

The immersion is an electrical way to heat your water, nothing to do with the gas. Because your boiler is on for three hours does not mean it is running for that time.
Have you checked the stat on the boiler? what is it set at?

DavyJones, as you suggested I tried opening the red wheeled valve futher last night and reduce the gas timer to 2hrs 20mins this morning. This sufficiently heated the water for two showers this morning. For tomorrow morning I'll try reducing the gas timer even further and will see how we get on.

Realistically, with everything working 100%, how long should we need to have the gas timed on for in order to heat the water for 2 pumped showers (roughly 20 mins of running time needed in total)? I would have assumed that an hour of gas would be sufficient but I have not dealed with gas before.

AlroD said:

DavyJones, as you suggested I tried opening the red wheeled valve futher last night and reduce the gas timer to 2hrs 20mins this morning. This sufficiently heated the water for two showers this morning. For tomorrow morning I'll try reducing the gas timer even further and will see how we get on.

Realistically, with everything working 100%, how long should we need to have the gas timed on for in order to heat the water for 2 pumped showers (roughly 20 mins of running time needed in total)? I would have assumed that an hour of gas would be sufficient but I have not dealed with gas before.

Click to expand...

Is the tank properly insulated. We just heat it in the morning so we have hot water for the showers, washing machine, kitchen etc....We dont try to regulate it...

Hi Suzie. Yes, the tank is fully insulated.

AlroD,
There are quite a few factors to consider, How big is the cylinder? standard cylinder is 30" x 18" and holds about 130L of water.

So it may take 60-90 mins(boiler will cycle on/off over this period and will not be running all the time) to heat it (85%),

depending on your pump, it could be pumping up to 20L a minute and half of this water is hot. So 10 minutes in the shower is 100L of hot water used approx.

If you let me know shower/pump and size of cylinder I think it could be worked out exactly.

If you have a strong pump, try adjusting flow rate at shower so it isn't on full whack or get a bigger cylinder.

Hi DavyJones,

I checked it out and our cylinder seems to be a standard size alright (approx 30" x 18").

The pump can can pump a maximum of 14 litres per minute so I see where you are coming from alright.

We turned down the pump setting on the shower down to 3/4 which is still giving pretty good pressure and this morning we got two decent showers out of the gas boiler being on for 1 hour and 30 mins. I guess we'll just have to go on trial and error to see what our optimal boiler timing should be. At least we seem to be getting somewhere!

One last thing to try for anyone having a similar problem. The thermostat on the hot water tank is usually held on by an elastic which holds the temp sensor part against the tank wall. This should be placed about one third of the way up the tank. If it is near the top, it will assume the desired temp has been reached when in fact only the top portion of your tank will be hot. Leaving it on for 3 hours will gradually heat more of the tank but not effficiently. The Bath/Sink switch has no effect when using the gas boiler to heat water, it only work in conjunction with the electric emersion. With regard to timer switches for Imersions, they can be purchased at most heat merchant and are easily fitted, most come with a digital timer and a 1/2 hour "boost" button, so no more forgetting to turn off the emersion! Night saver electricity will only work if your tank is factory lagged, that is where the tank ha been insulated with moulded insulating material, this has a very high insulating effect. Standard lagging jackets do not offer the same level of insulation and you lovely hot water will be cold by lunch time
If both you radiator and hot water are slow to heat, it is worth getting the system serviced, get the rediators balanced and a power flush of the system completed, chemical should also be added which will prevent clogging and corrosion in the future. Be sure to get at least a 6 month warranty on the work in writing as there can be residual problems with dirt/debris clogging the boiler pump following a power flush, particularly when it has not been done for some time. At the very least hold back part payment for 1 month, while heating system is in use (dont get it done at the start of Summer!)